1. Field of the Invention
The present invention relates to a substrate processing apparatus which supplies a processing liquid upon one major surfaces of variety types of substrates such as a semiconductor wafer, a glass substrate for photomask, a glass substrate for liquid crystal display, a glass substrate for plasma display and an optical disk substrate (hereinafter simply referred to as “substrates”) and subjects the major surfaces to predetermined substrate processing, and also to a substrate processing system which comprises such an apparatus.
2. Description of the Related Art
Known as this type of substrate processing apparatus is a substrate processing apparatus in which a substrate is held horizontally for instance, processing liquids such as a photoresist liquid, a cleaning liquid, a rinsing liquid and an etching liquid are supplied to the upward facing one (top surface) of major surfaces of a substrate, and the top surface is subjected to predetermined substrate processing. Such a substrate processing apparatus is described in Japanese Utility Model Application Laid-Open Gazette No. H2-137029, Japanese Patent Application Laid-Open Gazette No. H5-283327, U.S. Pat. Nos. 6,022,484 and 5,762,751. In these apparatuses, a substrate is placed on a rotating stage and thus held horizontally. Substrate processing is executed while a bottom surface of the substrate is held in contact with the rotating stage. Hence, a problem that the bottom surface of the substrate is damaged or contaminated could arise in some cases.
Against this background, a technique of holding a substrate as it is lifted up from a rotating stage has been proposed over the recent years. In a substrate processing apparatus according to the proposal, a plurality of substrate holding pins are disposed upright on the rotating stage which seats a substrate and the substrate is positioned and held at an edge of the substrate with these substrate holding pins. As the substrate showered with a processing liquid rotates, the processing liquid spreads all over a top surface, and the surface of the substrate is processed uniformly.
In this manner, since the substrate is held as it is slightly lifted up from a surface of the rotating stage in the conventional apparatus, it is possible to obviate a damage, a contamination and the like of the other major surface (bottom surface) of the substrate which would otherwise occur as the substrate is placed on the rotating stage in contact with the rotating stage. However, this gives rise to a different problem that a mist of the processing liquid splashed around during the substrate processing flies beneath and adheres to the bottom surface of the substrate and the bottom surface of the substrate is consequently contaminated.
To deal with this, techniques which require to dispose a member between a substrate and a rotating stage (Japanese Patent Application Laid-Open Gazette No. H5-114554) or to dispose a vertically movable member (Japanese Patent Application Laid-Open Gazette No. H7-130695 ( 2,845,738), U.S Pat. No. 5,601,645) have been proposed as a solution to the problem above.
By the way, the flying of the mist beneath the substrate is caused by a gap which is created between the bottom surface of the substrate and a periphery edge of a member. Hence, there is a significant relationship between the gap and the flying of the mist. However, while aiming at prevention of the flying of the mist by disposing the member close to the bottom surface of the substrate, the apparatus according to the proposal does not give any special consideration regarding the size of the gap. Due to this, this apparatus does not necessarily realize a sufficient preventive effect.
In addition, although it is desirable to dispose the member as close as possible to the bottom surface of the substrate for a better effect of preventing the flying of the mist, there naturally is a limit to dispose the member at the closest possible position because of bending of the substrate, a dimensional error of the member, an accuracy of assembling the apparatus, etc. Further, when a space between the member and the substrate is negatively pressurized, the mist is whirled into this space and adheres to the bottom surface of the substrate, the member and the like.
Meanwhile, when the gap between the substrate and the rotating stage is made as narrow as possible, it is difficult to use a transportation mechanism which is widely used. This is because of a fact that such a transportation mechanism inserts a transportation arm which holds a substrate into a space which is defined between the rotating stage and other major surface of the substrate and then places the substrate on substrate holding pins. Hence, a reduction of the gap between the substrate and the rotating stage leads to a restriction that a special transportation mechanism is required for transpiration of a substrate, which in turn lowers the versatility of the substrate processing apparatus.
In addition, in the apparatus according to the proposal, e.g., the apparatus described in Japanese Patent Application Laid-Open Gazette No. H7-130695 (U.S. Pat. No. 2,845,738), an outer shape of the vertically movable member is a perfect circle and the vertically movable member is formed slightly larger than a substrate. Hence, a periphery edge of the vertically movable member sticks out beyond the substrate and is exposed to the mist-splashed atmosphere (around the substrate). As a result, the mist created during the substrate processing is kicked back by the periphery edge and jumps toward the bottom surface of the substrate in some cases.
Further, while Japanese Patent Application Laid-Open Gazette No. H7-130695 (U.S. Pat. No. 2,845,738) describes to set the size of the vertically movable member approximately equal to the size of a substrate, this may also give rise to the following problem. That is, a substrate processed with this type of substrate processing apparatus often has a special shape. For example, in the case of a semiconductor wafer which serves as a substrate, there is a nick portion such as a notch and an orientation flat which indicates a crystallographic reference orientation within the plane of the wafer. In other words, a semiconductor wafer is obtained by forming a nick portion at a periphery edge of a semiconductor substrate which has a disk-like shape, and therefore, an outer shape of the semiconductor wafer is not a perfect disk but is generally disk-like. On the contrary, in the apparatus described in Japanese Patent Application Laid-Open Gazette No. H7-130695 (U.S. Pat. No. 2845738) in particular, the outer shape of the vertically movable member is a perfect circle and the size of the vertically movable member is about the same as that of a substrate. Hence, a part of the vertically movable member is exposed to the mist-splashed atmosphere (around the substrate) through the nick portion. As a result, the mist created during the substrate processing is kicked back by the exposed part and jumps toward the bottom surface of the substrate in some cases.